Efficiency
What is "waste" energy?
Output energy that isn't useful.
What is the formula for calculating kinetic energy?
Ek=0.5mv2
What is the formula for Graviational PE?
EP=mgh
What is the law of conservation of energy?
Energy cannot be created or destroyed, only changed from one form to another or transferred.
A rock with a mass 5kg is placed on a wall 2m high, what is its Kinetic Energy?
0 J
How do you calculate total input energy?
Useful Output / Energy Efficiency (As decimal)
If you were to double the speed of an object what would it do to the total Kinetic Energy?
It quadruples
How do you calulate weight?
Mass x Gravity
What energy transformations occur from a wind turbine?
Mechanical -> Electricity
Who does more Work, Person A moving a 10kg bag of cement up 1m over 2 seconds or Person B holding a 10kg bag of cement above their head for 2mins?
Person A
How would you calculate the efficiency of an electric lightbulb. Identify the energy types in the formula.
Light energy output / Electrical energy Input x 100
A 0.5 kg ball is travelling at 4 m/s. Its kinetic energy is:
4 J
Ethan trips down a cliff and lands in water with 1500J of energy if his mass is 70kg, what height did he fall from?
2.19m
If a ball falls from 10m high, at 5m high what would the ratio of PE to KE be?
50/50 or 1:1
What does it mean for work to be done in terms of energy?
The force required to move an object over a distance.
A blender uses 300 J of electrical energy and produces 210 J of useful kinetic energy in 5 seconds. What is it's efficiency?
70 %
What is the speed of an object with a weight of 28.42N and 16J of Kinetic energy?
3.3m/s
A 2kg cat jumps from 1m high table onto a shelf 2m above the table, what is its GPE?
58.8 J
Explain why a pendulum eventually stops moving, even though energy is “conserved”.
Some mechanical energy is transformed into heat and sound due to air resistance and friction at the pivot — total energy remains constant, but less remains as useful mechanical energy.
A student does 400 J of work climbing a ladder in 8 s. What power is produced?
50 W
A motor does 1500 J of useful work and wastes 500 J as heat.
What is the total input energy?
2000 J
A 0.5 kg ball falls from a height of 8 m.
Find its velocity just before impact.
12.5 m/s
A 950 kg small car is hoisted on a service lift from 0.5 m to 1.6 m.
Increase in GPE?
10,241 J
A 2 kg cart rolls down a ramp. At the top, Ep = 30 J and Ek = 0 J.
At the bottom, Ep = 5 J. Find the kinetic energy at the bottom.
25J
A 60 kg student climbs stairs 3 m high.
Work done = ?
1764 J